On The Importance Of Keeping Slime Away
Something to think about for the summer.
Where are you leaving your boat between regattas ?
How much will be growing on the bottom when you get back to it ?
Its All About The Local Flora And Fauna
Weed and other marine wildlife, whose main aim in life sometimes seems to be to slow us down, grow at different rates depending on a whole host of variables, everything from how sunny a spot the boat is parked in to the time of year.
Even over the course of a day marine life will start to stick to the bottom of your boat.
It starts as slime, the slime that the fish that live in marinas like to scrape off the bottom of the boat, other creatures then stick to the slime and from there its a not so slippery slope to an entire Zoo living on the bottom.
Our experience at Dartmouth this year was a classic case of not planning for this effect.
We did the JOG Cowes Torquay race in mid August then left Jengu in the excellent care of Noss On Dart Marina staff upstream from Kingswear on the river Dart for a couple of weeks prior to Dartmouth week.
We had the boat in a safe, secure berth in the right location and at reasonable price; what could go wrong ? At least one of the crew had a fabulous week working from boat appreciating the quiet tranquillity of the location.
For those of you who know Kingswear you will understand that its the sunny side of the river Dart. Jengu was parked on one of the outside pontoons in deeper water.
It was a typical August in Devon, warm and sunny with showers. Noss Marina is higher up the the Dart so the water is more brackish where the tidal sea water mixes with the water flowing down the river; down from the heights of Dartmoor through rural South Devon.
According to the Dart Harbour authority website;
“The dissolved inorganic nitrogen level in the estuary is classified as Moderate. This is principally due to farming practices – livestock, soil and nutrient management, as well as waste water discharges, though leisure boating does play its part as well. South West Water are working hard to reduce these discharges, and many local farmers are also improving their ways of working.” https://www.dartharbour.org/the-dart-estuary/water-quality/
So basically we left Jengu in a lovely spot, particularly lovely if you are the type of wildlife that likes to live on the bottom of a slow moving or stationary boat, loves a bit of sunshine and plenty of nutrients; especially if a gently flowing river is bringing a fresh supply of those nutrients on a regular basis.
What Weed And Slime Does To Boat Performance
Jengu was 7th overall and 2nd in IRC 2 for the JOG Cowes Torquay race. A race that was blessed with light winds. So on the 14th August we had a boat that was quick in light airs.
Three weeks later we headed out for the first day of Dartmouth Regatta.
We had already missed the passage race due to an issue with the boats forestay so the previous day had involved a lot of running around looking for spare parts with people climbing forestays …. that sort of thing. The conditions on the Thursday though were perfect, sunshine, blue sky and a gentle breeze. We were all very relaxed, confident even.
We got to the start of the first race, we were in an OK position on the line, half a knot of tide against us holding us back from the line, we powered up the boat in the count down to the start ready to take off up the first beat and nothing happened.
When you are in a 9 boat fleet in light conditions and you don’t make it off the line you end up sitting in all the dirty disturbed turbulent air from the rest of the fleet. We actually started going backwards.
Looking back my recollection is of us still struggling to get over the line while the race officer started the next race 5 minutes later.
The second race wasn’t much better.
We were fourth overall at Dartmouth in 2021. This wasn’t the set of results we were looking for.
Rule 14 aka Racing Rules Of Sailing Appendix L Sailing Instructions Guide Item 25
“Boats shall not be hauled out during the event except with and according to the terms of written permission of the OA. This restriction also applies to the use of underwater breathing apparatus around boats between the preparatory signal of the first race and the end of the event. Advisory note: The use of underwater breathing apparatus at any time requires Harbour Authority”
For the last 6 seasons we have used an eroding anti fouling product from International.
It is absolutely brilliant in that we leave Gosport heading to Cowes on a Friday night doing 7 knots under engine and by the time we get to Cowes we have gained an extra knot as the wild life slides off the hull.
It does however have a number of drawbacks.
Its is disgusting to sand down with wet and dry paper. We used black antifoul. You end up with a black paste on the wet and dry paper and generally on everything else.
If you pressure wash the hull you take a lot of the anti foul off. Or at best you redistribute it around any down wind boats.
If the boat sits in the mud, some marina berths are shallower than others the inside berths at East Cowes being a case in point, it takes the anti foul off the bottom of the heel.
If you go swimming and touch the boat the anti foul transfers to you.
Common sense also suggests the particles that get eroded off the hull when the boat moves through the water are more than likely micro plastics that are entering the environment in an uncontrolled manner. Andrew Turner talks about the role of paint derived micro plastics in his paper for Plymouth University here;
So we switched to a hard anti foul at the start of the 2022 season.
We acknowledged the boat would need a lift out and scrub off but Haslar now has a Boat Lift that can do a reasonably speedy turn around on a quick hose down so that wasn’t an issue. We did a half season lift and scrub before the RORC St Malo race and the result gave us a boat with a very slippery hull …. it certainly felt like that on the run into St Malo ghosting through a stationary fleet on our own personal breeze.
The boats performance at Cowes week wasn’t amazing but we put that down to our inexperience working together as a crew. JOG Cowes Torquay race result suggests at that point the hull was fine.
We are fortunate enough to sail with an ex-BBC drone operator. One Go Pro camera on the end of an extendible boat hook was enough to confirm that we had a veritable reef growing on the bottom of the boat. We needed to shift some of the wildlife if we were going to make any progress.
Lets go to the boat lift and get a scrub.
Rule 14 in the sailing instructions says no. No diver allowed either.
Time to get the broom out and start scrubbing.
So Did All The Scrubbing Work ?
Well sort of.
Track one on the left is race one on the Thursday. Track two on the right is actually the bay race on the Saturday.
We use Rockit to monitor the boats perfomance. Rockit tracks the boat and analyses the performance based on the data from the navigation instruments; GPS, Wind etc.
So we know the wind conditions when the boat is sailing and we know what fast looks like .. and slow.
So if we look at any singular set of data we can give a percentage of the best sample data. On the Jengu scale. Pink is best, Blue is way off the pace; sub 60% of the target speed based on previous performance.
So on the first day we were travelling around the race course at significantly less than our previous best performance.
If you click on the image you can expand it; you can see that some of the segments in the track are in the 40% range. We weren’t towing a bucket we checked that and just about everything else over the next 3 days.
The third days track is mostly greens, 90-99% of target and oranges 80-89% of target. There are some blues but they are mostly in the corners and could be explained by gybes and tacks, hoists and drops.
So yes the scrubbing made a difference and on the third day we weren’t nearly as slow; were quick enough to pick up a place in the rankings.
So What Would We Do Differently ?
Progressing requires an understanding of why things didn’t go right the first time and changing the bits that don’t work. Its important not to expect a different result when you keep doing the same thing.
Point One : A clean bottom is really important.
For 2023 we have stuck with the Hard Antifouling strategy.
Talking to various other skippers around the Solent a couple of things become apparent. The fast boats either dry sail or scrub the boat on a regular basis through the season. One boat allegedly scrubs before each race weekend.
We have organised ourselves a bulk purchase of boat lifts and scrubs from the boat lift. We will do that before each major event so six or seven times March to October.
We haven’t re applied the anti foul over the winter. It looked smooth even if it clearly wasn’t deterring much of the wildlife. The literature that came with the anti-foul suggested it was good to two seasons anyway.
Its more or less the same price to do the seven lifts as it is to pay someone to anti foul the boat. Particularly when you factor in the cost of storage ashore.
Point Two : We need to go on a diet and probably the boat needs to as well.
We spent a lot of time rafted with the other J109’s at Dartmouth. A couple of things became very obvious from nosing around (its important to check out what the opposition are doing).
We have a lot more gear on the boat than some of the other boats. I was surprised to find that one of the boats at Cowes week only had a Main, Jib and A2 spinnaker and no other sails like a big dinghy; for round the cans racing they were able to reduce what they carried back to a bear minimum. The same went for a lot of the running rigging why have two jib and spinnaker halyards if you are going to hoist on the port one most of the time ?
Having taken a lot of stuff off the boat prior to racing at Dartmouth I can see this would make a considerable difference. We filled two family sized cars with surplus gear.
There is definitely an argument for physically emptying the boat at the end of each season and making sure only whats needed goes back on board in the Spring.
A shed at the marina or some kind of nearby storage unit is also on the agenda. There is a lot of equipment we carry for offshore racing that we don’t need to race around the cans in the Solent; the life raft being one of the obvious items. Taking it off and storing it will save on wear and tear as well.
Then there is the beer in the fridge. How many cans are essential ?
A Postscript To This Article
As a footnote; when we brought Jengu back to Gosport at the beginning of September we put her on the Sea Lift at Haslar and had a look at what was growing.
The video attached shows what was living on the bottom.
This is roughly two months on from the previous lift and scrub. Jengu had also been sailed the 100 odd miles back from Devon the previous weekend and been attacked the broom a week to 10 days prior. You can see there is a lot of growth on the hull; particularly the rudder blade.
After a good clean up we put Jengu back in the water. The crew then took Jengu to the JOG Cowes Poole Race the following weekend and managed 5th in IRC 2 and 15th overall out of 40 odd finishers; so we were back to the boat speed we saw back in early August.
Want To Know More ?
If you would like to talk about how you might be able to use Rockit to better understand boat performance click the button below to get intouch.